Power supply method for electrical equipment

ABSTRACT

A power supply method an apparatus for powering electrical equipment, the electrical equipment operated by using current peaks. The electrical equipment may be connected via at least one capacitive element to a voltage converter which may be connected to a storage battery. The voltage converter may be current-regulated from a reference current. The reference current may correspond to an average current between two peaks (generally corresponding to one cycle of operation). The reference current may be calculated in a predictive manner and the reference current may include a correction factor. The voltage output from the voltage converter may be maintained between an upper limit and a lower limit.

FIELD

The present application relates to a method of powering electricalequipment such as an electromagnetic actuator suitable for use inparticular in actuating valves in the engines of motor vehicles.

BACKGROUND

Such an electromagnetic actuator is incorporated in a power supplynetwork in which it is connected via a capacitive element to a voltageconverter which is itself connected to a storage battery and to analternator and which is voltage-regulated and current-limited.

In a network of this type, operating the electromagnetic actuator givesrise to current being drawn from the network at the outlet of thevoltage converter, with this effect being transferred to the inlet ofthe voltage converter. This gives rise to current peaks ofcharacteristics which are incompatible with the response time of thealternator, such that the alternator cannot deliver the necessarycurrent, so the current is taken from the storage battery.Unfortunately, these high-amplitude current peaks cause the storagebattery to become heated, thus making standard batteries relativelyunsuitable for such use.

It might be thought that such current peaks could be filtered byincreasing the capacitance associated with the voltage converter.Unfortunately, given the amplitude and the duration of such peaks, suchfiltering would require capacitors of large volume in order to beeffective. It would also be possible to use a storage battery having lowinternal resistance or an alternator having a short response time. Suchelements are nevertheless relatively expensive.

SUMMARY

One embodiment provides means that are inexpensive and effective forpowering such electrical equipment optimally.

To this end, the embodiment provides a power supply method for poweringelectrical equipment operating on current peaks and connected via atleast one capacitive element to a voltage converter connected to astorage battery, the voltage converter being current-regulated from areference current corresponding to a mean current between two peaks.

Thus, current regulation of the voltage converter which is controlled inthis way as a current generator enables a substantially constant valueto be maintained for the current delivered by the storage battery to theinput of the voltage converter. This makes it possible to minimize thevolume of the capacitive element.

In a particular implementation, the mean current is evaluated inpredictive manner on the basis of actuator control data.

The reference current is thus obtained in anticipation. This mode ofcalculation makes it possible to obtain the reference current in simplemanner and to avoid using as the reference a current as measuredperiodically, which would require regulation to be fast and wouldrequire high capacitance in order to act as a supply of energy in theevent of a sudden change in current.

In which case, the reference current is advantageously equal to theevaluated mean current plus a correction factor for a voltage at theoutput from the converter which is rising and less than an upper voltagelimit, and the reference current is equal to the evaluated mean currentminus the correction factor for a voltage at the output of the converterwhich is falling and greater than a lower voltage limit.

The correction factor is determined in such a manner that the currentinput to the converter is maintained within a determined range that iscompatible with the characteristics of the storage battery and thevoltage at the output from the converter is maintained in a determinedrange compatible with the characteristics of the equipment. This enablesthe frequency with which the reference is calculated to be limited.

Also advantageously, the correction factor corresponds to inaccuracy inthe evaluation of the mean current and is preferably equal to about 10%of the evaluated mean current.

The correction factor serves to compensate for any differences betweenthe evaluated mean current and the mean current as actually consumed.The correction factor thus enables a mean current range to be determinedwhich has a very high chance of including the value of the mean currentas actually consumed.

Other characteristics and advantages of the invention appear on readingthe following description of a particular and non-limitingimplementation of the invention and upon review of the claims.

BRIEF DESCRIPTION OF THE DRAWING

Reference is made to the sole accompanying FIGURE which is a diagram ofa power supply network used for powering electrical equipment.

MORE DETAILED DESCRIPTION

In this case, the method is intended for powering an electromagneticactuator suitable for actuating valves of a motor vehicle engine. Suchan actuator has electromagnetic coils which, when excited, attract anarmature secured to at least one valve in order to bring the valve intoan open position or a closed position and hold it in position. Thecurrent needed for exciting the coils must be delivered to them in theform of peaks of large amplitude and short duration at an excitationfrequency which is determined by a vehicle controller which determinesthe current to be fed to the actuator as a function of control data suchas the extent to which an accelerator pedal is depressed, the speed atwhich the engine is running, the speed of the vehicle, and moregenerally engine load parameters.

With reference to the FIGURE, the electromagnetic actuator 1 isconnected to a power supply circuit 2 which comprises a storage battery3 connected to a voltage converter 4. The battery 3 delivers a voltageof about 12 volts (V) and it is connected to an alternator (not shown)in order to be recharged. The voltage converter 4 is arranged to convertthe input voltage of 12 V to an output voltage of about 42 V.

The voltage converter 4 is connected to the electromagnetic actuator 1via a capacitive element 5 arranged to store the energy delivered by thevoltage converter 4.

The method consists in current regulating the voltage converter 4 on thebasis of a reference current corresponding to a mean current between twopeaks.

The mean current is evaluated in predictive manner on the basis of thevoltage on the storage battery 3 and the peak power that is to beconsumed over a predetermined cycle duration. This power depends on theengine speed which can be deduced from the actuator control data used bythe vehicle controller.

The voltage converter controlled in this way thus forms a currentgenerator which is servo-controlled to the mean power which is about tobe consumed during the following engine cycle.

Regulation is implemented conventionally by modulating the voltage atthe input to the converter as a function of the current measured at theoutput from the converter.

The voltage at the output from the converter is also measured, and isdelivered to the controller for use when determining the referencecurrent to apply a correction factor to the evaluated mean current.

The reference current is thus equal to the evaluated mean current plus acorrection factor for a voltage at the output from the converter whichis rising and which is less than an upper limit voltage, and thereference current is equal to the evaluated mean current minus thecorrection factor for a voltage at the output of the converter which isfalling and which is greater than a lower voltage limit.

This correction factor corresponds to uncertainty concerning the instantat which the next current peak will appear, i.e. to a possibledifference between the evaluated mean current and the mean currentactually consumed. The correction factor is equal to about 10% theevaluated mean current.

Because the voltage converter is controlled as a current generator, thevoltage at the output from the converter varies. It should be observedthat since the actuator is current-driven, variations in voltage are oflittle consequence. Nevertheless, these variations are set within therange defined by the lower and upper voltage limits. These limits aredetermined so that the corresponding voltage range is compatible withthe characteristics of the actuator. By way of example, if thecharacteristics of the actuator allow it to be operated with voltages inthe range 30 V to 50 V, then a lower limit is selected to be equal toabout 34 V and an upper limit is set to be equal to about 44 V.

Naturally, the invention is not limited to the implementation describedand variant implementations can be devised without going beyond theambit of the invention as defined by the claims.

In particular, the reference may be calculated on the basis of a currentthat is measured periodically.

Although the correction factor is equal to 10% in the example described,its value could be different. It is also possible to do without acorrection factor.

In addition, the lower and upper voltage limits can also be modified,and in particular they can be closer together or further apart as afunction of the characteristics of the equipment to be powered.

Furthermore, the invention is not limited to powering an electromagneticactuator, but can be used for powering any electrical equipment thatoperates in pulsed mode. For example, the invention may be applied to asystem for flashing vehicle headlights.

1. A power supply method for powering electrical equipment operating oncurrent peaks and connected via at least one capacitive element to avoltage converter connected to a storage battery, wherein the voltageconverter is current-regulated from a reference current corresponding toa mean current between two peaks.
 2. A power supply method according toclaim 1, wherein the mean current is evaluated in predictive manner fromcontrol data for the equipment.
 3. A power supply method according toclaim 2, wherein the reference current is equal to the evaluated meancurrent plus a correction factor for a voltage at the output from theconverter (4) which is rising and less than an upper voltage limit, andthe reference current is equal to the evaluated mean current minus thecorrection factor for a voltage at the output of the converter (4) whichis falling and greater than a lower voltage limit.
 4. A power supplymethod according to claim 3, wherein the correction factor correspondsto inaccuracy in the evaluation of the mean current.
 5. A power supplymethod according to claim 4, wherein the correction factor is equal toabout 10% of the evaluated mean current.
 6. A system for powering anelectrical device operating on current peaks in a vehicle having abattery, the system comprising: a voltage converter configured to becoupled to the battery of the vehicle; an electromagnetic engine valveactuator configured to be located in the vehicle and configured toreceive power from the voltage converter; and a capacitive elementconnecting the electrical device and the voltage regulator; wherein thevoltage converter is regulated such that power may be drawn from thebattery in a manner compatible with the properties of the battery. 7.The system of claim 6, wherein current to be provided to the voltageconverter is determined in a predictive manner.
 8. The system of claim6, wherein current to be provided to the voltage converter is determinedbased on an average amount of power used by the electromagnetic enginevalve actuator.
 9. The system of claim 6, wherein the voltage outputfrom the voltage converter is maintained between an upper limit and alower limit.
 10. The system of claim 9, wherein the lower limit is noless than about 30 V and the upper limit is no more than about 50 V. 11.The system of claim 10, wherein the lower limit is about 34 V and theupper limit is about 44 V.
 12. A system for powering an electricaldevice operating on current peaks in a vehicle having a battery, thesystem comprising: a voltage converter configured to be coupled to thebattery of the vehicle; an electrical device configured to be located inthe vehicle and configured to receive power from the voltage converter;wherein the voltage converter is current-regulated.
 13. The system ofclaim 12, wherein the electrical device is a vehicle headlight.
 14. Thesystem of claim 12, further comprising a capacitive element connectingthe electrical device and the voltage regulator.
 15. The system of claim12, wherein the electrical device is an electromagnetic actuator. 16.The system of claim 15, wherein the electromagnetic valve actuator isconfigured to actuate an engine valve.
 17. The system of claim 12,wherein the voltage output from the voltage converter is maintainedbetween an upper limit and a lower limit.
 18. The system of claim 17,wherein the lower limit is no less than about 30 V and the upper limitis no more than about 50 V.
 19. The system of claim 18, wherein thelower limit is about 34 V and the upper limit is about 44 V.
 20. Thesystem of claim 12, wherein the voltage converter is current-regulatedfrom a reference current.
 21. The system of claim 20, wherein thereference current corresponds to a mean current between two peaks. 22.The system of claim 20, wherein the reference current is evaluated in apredictive manner.
 23. The system of claim 22, wherein datacorresponding to engine speed is used to evaluate the reference currentin the predictive manner.
 24. The system of claim 20, wherein thereference current corresponds to an average amount of electricityconsumed by one or more electrical devices receiving power from thevoltage converter.
 25. The system of claim 24, wherein the referencecurrent includes a correction factor.
 26. The system of claim 25,wherein the correction factor is about 10% of the average amount ofelectricity consumed.